Function root_cache_dir 

pub fn root_cache_dir() -> PathBuf

Root cache directory for all enrichment sources, i.e. …/sbom-tools.

This is the parent of every per-source namespace directory; the cache subcommand uses it to enumerate, size, export, and import the cache as a whole. Falls back to a .cache-relative path when no platform cache directory is available, matching namespaced_cache_dir.